Changes in Ecosystems: Ecological Succession

1. Changes in Ecosystems:Ecological Succession

2. Ecological Succession • Ecosystems are constantly changing in response to natural and human disturbances. • As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. • Ecological Succession – Series of predictable changes that occurs in a community over time

3. Some Causes of Ecological Succession • Can result from slow changes in the physical environment or from sudden disturbances (either natural or man made). • Some causes include: • Clearing land • Climate change • Introduction of nonnative species • Natural disasters such as volcanic eruptions, forest fires, hurricanes, & floods

4. Succession: • Natural, gradual changes in the types of species that live in an area; can be primary or secondary • The gradual replacement of one plant community by another through natural processes over time

5. Primary Succession • Begins in a place without any soil • Sides of volcanoes • Landslides • Flooding • Starts with the arrival of living things such as lichens that do not need soil to survive • Called PIONEER SPECIES

6. http://botit.botany.wisc.edu http://www.saguaro-juniper.com/

7. Primary Succession • Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces • When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

8. http://www.life.uiuc.edu

9. Primary Succession • Simple plants like mosses and ferns can grow in the new soil http://www.uncw.edu http://uisstc.georgetown.edu

10. Primary Succession • The simple plants die, adding more organic material • The soil layer thickens, and grasses, wildflowers, and other plants begin to take over http://www.cwrl.utexas.edu

11. Primary Succession • These plants die, and they add more nutrients to the soil • Shrubs and tress can survive now http://www.rowan.edu

12. Primary Succession • Insects, small birds, and mammals have begun to move in • What was once bare rock now supports a variety of life http://p2-raw.greenpeace.org

13. Mount St. Helen Before Eruption in 1980

14. Mount St. Helen 6 Years After Eruption Mount St. Helen After Eruption Mount St. Helen 19 Years After Eruption Mount St. Helen 10 Years After Eruption

15. Secondary Succession • Begins in a place that already has soil and was once the home of living organisms • A disturbance of some kind changes an existing community • Occurs faster and has different pioneer species than primary succession • Example: after forest fires

16. http://www.geo.arizona.edu

17. http://www.ux1.eiu.edu

18. Climax Community • A stable group of plants and animals that is the end result of the successionprocess • Does not always mean big trees • Grasses in prairies • Cacti in deserts